1. Field of Invention
This invention relates to wireless communication for control of fume hoods.
2. Discussion of Related Art
Fume hoods are commonly used in school and industry settings for handling potentially harmful materials, particularly substances that give off noxious fumes. A typical fume hood includes a housing within which the harmful materials may be stored and used. Users may access the interior of the housing through an opening, which in some hoods may be opened and closed by one or more movable sashes. The housing is vented so that air and potentially harmful gases or other materials in the housing are exhausted through ductwork. Fresh air is drawn in through the hood opening to help keep potentially harmful materials contained, i.e., prevent harmful materials from exiting the hood through the opening into the space where people may be located.
Proper control of airflow through the hood opening may be important for safety, economic, comfort or other reasons. For example, if airflow through the hood opening is too low (e.g., the velocity of airflowing through the opening or face velocity is too low), contaminants inside the hood may have an opportunity to exit the hood through the opening. However, maintaining a high volume airflow through the hood opening at all times may be wasteful because unnecessarily large volumes of conditioned air (e.g., cooled or heated air) in the room may be drawn into the hood and exhausted from the building. As a result, additional air must be conditioned and supplied to the room to replace the exhausted air. Some hood control systems lower the airflow or face velocity of air at the hood opening in certain conditions, such as when the hood opening is closed or nearly closed or when the hood is not being used. Airflow is then increased when the opening is enlarged and/or if the hood is in use. Such control systems are well known and are described, for example, in U.S. Pat. Nos. 4,706,553; 4,893,55 1; 5,117,746; 4,528,898 and others. These patents describe various systems for detecting a hood opening size, such as by detecting sash position, and using the hood opening size to control flow through the hood. For example, some of these systems use one or more sensors to detect the position of one or more sashes and send this information by a wired connection to a fume hood control which then uses the information to control airflow in the hood.